1°) Introduction

Edmond Halley was about 20 years old when he suggested that the transit of a planet across the disk of the Sun might enable the distance of the Sun to be determined. Ahead of him was an illustrious career in which he would influence almost every branch of science.


The first observed Transit of the Planet Venus predicted & observed by Jeremiah Horrocks, 24th November 1639 - Artist: J. W. Lavender 1903 - Image provided by Astley Hall Museum & Art Gallery, Chorley

At about the same age, more than a century before, Jeremiah Horrocks predicted and then observed the 1639 transit of Venus. From this observation he deduced a value for the Sun's distance, which was four times greater than hitherto thought. A memorial plaque in Westminster Abbey (London), erected in 1874, eloquently records his achievements:

“In memory of Jeremiah Horrocks
Curate of Hoole in Lancashire
Who died on the 3rd of January 1641 in or near his 22nd year
Having in so short a life
Detected the long inequality in the mean motion of Jupiter and Saturn
Discovered the orbit of the Moon to be an ellipse
Determined the motion of the lunar apse
Suggested the physical cause of its revolution and predicted from his own observations the Transit of Venus which was seen by himself and his friend William Crabtree
On Sunday the 24th of November (OS) 1639."

Such discoveries, at so young an age, held out great promise for his future achievements. It is no wonder that Sir John Herschel later called him the “pride and boast of English Astronomy” and J-L Delambre compared his genius to that of Kepler.

Tragically, Horrocks did not get the chance to fulfil his great potential. After completing his treatise on the transit of Venus he arranged to meet his friend William Crabtree to discuss its publication. The day before the intended meeting, on 4th January 1641, however, he suddenly died. There is no surviving record of the cause of death. His work was only known to a small number of people and most of his papers were lost when he died. Fortunately, his treatise on the transit - Venus in Sole Visa - eventually found its way to the germano-polish astronomer Hevelius, who published it in 1662. The Royal Society in London eventually published the surviving works of Horrocks in 1672, more than 30 years after their author’s demise.

The result of his early obscurity and his young death is that the life of Jeremiah Horrocks is an enigma. On the basis of meagre information later generations of admirers have embellished the details. In doing so, they have often gone beyond what can be proven.

Although the Westminster Abbey memorial claims that Horrocks was a Curate in Hoole, there is no real evidence to prove this. It is true that Horrocks was a very pious youth: his religious conviction is clear in every part of Venus in Sole Visa. On the day of the transit, which was a Sunday, according to Horrocks "I watched carefully … from sunrise to nine o'clock, and from a little before ten until noon, and at one in the afternoon, being called away in the intervals by business of the highest importance which, for these ornamental pursuits, I could not with propriety neglect." This single statement is what has led many people to think that Horrocks was a clergyman with a service to conduct. In the seventeenth century, however, one would not need to be a clergyman in order to feel an unavoidable obligation to go to Church on the Christian Sabbath. Moreover, the young astronomer was not old enough to be ordained. No record of his ordination exists and the post of curate was at that time occupied by someone else.